[laynlo15]

Mine said 26.83 or something like that. I didn't really understand that since our stock tires in the rear are 27.75 or something like that.

[PRAY]

Originally Posted by laynlo15

Mine said 26.83 or something like that. I didn't really understand that since our stock tires in the rear are 27.75 or something like that.

It said 26.83 cause that is the actual rear tire height. If you use the aspect ration it is labeled as a 27.5. Actual tire heights are hardly ever as labeled and every manufactures tires seem to be different actual size than the aspect ratio states. It is like dudes shoes or chicks jeans size. Not all size 10's are created equal. The way I check is to lay a straight edge across the top of the tire and measure up to it from the ground at the center of the wheel at full inflation. I guess you could also roll out the tire and divide by pi. Not sure if those would be the same measurement. But the rpm to mph math for this cars speedometer and all of its commanded shift points is based off of 26.83. I doubt GM would have screwed this up and sold a bunch of cars that are actually going much faster than the speedo is registering. The above relates to radials. I don't have a good method to compensate for the growth factor of slicks.

[cwebster]

Could someone tell me specifically, exactly where and how in the menus these tire height settings can be changed? I looked everywhere I could think of when I was at the track and could not find them. In the back of my mind I'm wondering if the ECM is pulling power when I'm trying to get fast on my new MT Street tires. I measured 27 3/4" diameter on the new wheels (24 PSI) lying flat on the driveway, using a framing square and straight-edge. I measured to the highest point mid-tread.

[PRAY]

Originally Posted by cwebster

Could someone tell me specifically, exactly where and how in the menus these tire height settings can be changed? I looked everywhere I could think of when I was at the track and could not find them. In the back of my mind I'm wondering if the ECM is pulling power when I'm trying to get fast on my new MT Street tires. I measured 27 3/4" diameter on the new wheels (24 PSI) lying flat on the driveway, using a framing square and straight-edge. I measured to the highest point mid-tread.

In HPT go to EDIT and select Gear/Tire Wizard. You can make your changes there.

[cwebster]

Originally Posted by PRAY

In HPT go to EDIT and select Gear/Tire Wizard. You can make your changes there.

I don't know what HTP means and I didn't see an EDIT button in any of the screens I looked at. Is this under the "Settings" icon on the Infotainment system or maybe the left-arrow "Options" menu in the DIC? Please be specific.

Thanks!

--Cal

[PRAY]

Originally Posted by cwebster

I don't know what HTP means and I didn't see an EDIT button in any of the screens I looked at. Is this under the "Settings" icon on the Infotainment system or maybe the left-arrow "Options" menu in the DIC? Please be specific.

Thanks!

--Cal

Horse Power Tuners. Sorry bro, there is nothing in the car you can do to adjust. It has to be done with a Tech II device or one of the aftermarket tuning software programs.

[cwebster]

Originally Posted by PRAY

Horse Power Tuners. Sorry bro, there is nothing in the car you can do to adjust. It has to be done with a Tech II device or one of the aftermarket tuning software programs.

Ahh... okay. Well, I guess it's a good thing my DR setup is very close to stock in terms of wheel height. There's probably no ECM intervention for different wheel height. I just wanted to be sure to keep intrusions to a minimum.

Thanks for clearing that up.

--Cal